1. Field of the Invention
This invention relates in general to electronic devices, and more particularly, to electronic devices comprising digital-to-analog (“D/A”) converters and methods of using those electronic devices.
2. Description of the Related Art
Organic electronic devices have attracted considerable attention since the early 1990's. Examples of organic electronic devices include Organic Light-Emitting Diodes (“OLEDs”), which include Polymer Light-Emitting Diodes (“PLEDs”) and Small Molecule Organic Light-Emitting Diodes (“SMOLEDs”). Display devices, including OLED displays, have played an important role in modern human life. As computing, telecommunications, home entertainment, and networking technologies converge, the display unit will become more important.
In the display area, there are many kinds of technologies including cathode ray tube (“CRT”), liquid crystal display (“LCD”), and so on. LCD technology is dominant in the present flat panel display market. However, as display size increases, this technology has some issues with the backlight and power consumption. OLED technologies have great potential advantages over other display technologies, especially in larger size displays.
OLED material lifetime is a concern, however. Organic active layers, when used in radiation-emitting electronic components, have a finite lifetime. After a long time of driving a stationary image, inhomogeneity and decay of emission intensity can occur due to different driving (stress) conditions at the organic electronic level.
A compensation mechanism can be used to extend the lifetime of an OLED display as the OLED material degrades. One compensation scheme can use peripheral driving electronics within the peripheral circuitry. Row drivers and data drivers, as parts of the peripheral electronics, are used to turn on the display. FIG. 1 includes a block diagram of conventional data driver 100. R, G, and B data, from external digital video inputs for Red, Green and Blue electronic components, are received by data control unit 102 and are routed to the data latch unit 122. An address shift register 104 receives an external enable signal, a shift direction signal, and a shift clock signal. The external enable signal is used to enable the address shift register 104. The shift direction signal controls the shift direction (from scan line 1 to scan line n or from scan line n to scan line 1). The shift clock signal provides a reference timing signal from which activities in the conventional data driver 100 can be coordinated. The data latch unit 122 also receives a latch enable signal and a load signal. The data latch unit 122 may or may not include storage registers. If storage registers are present, data can be transferred from individual data latches to their corresponding storage registers. The latch enable signal is used to enable individual data latches (or storage registers, if present) within the data latch unit 122, and the load signal enables the captured datum for each data latch to be output to D/A converter 124. The D/A converter 124 also receives a gray scale reference signal, which controls the D/A converter relationship and obtains suitable gamma correction for the display. Outputs from the D/A converter 124 are received by output-signal drivers 126, which can send data along data lines to electronic components within an array of a display.
A brief of overview of the operation of the data driver 100 is given below. The address shift register 104 produces scan signals from scan line 1 to scan line n (or scan line n to scan line 1) as determined by the shift direction signal. The data latch unit captures the input R, G and B data pixel by pixel, controlled by the scan signal from address shift register 104, until a whole row of data are recorded into data latch unit 122. The recorded row data is output from data latch unit 122 and received by D/A converter 124 when a load signal is received by the data latch unit 122. The D/A converter 124 changes the digital signals received from the data latch unit 122 into analog signals and outputs them to the output-signal drivers 126, which in turn sends analog signals to the display. Conventionally, the D/A converter 124 has a fixed Vmax (maximum analog output voltage) and a fixed Vmin (minimum analog output voltage). Vmax and Vmin do not change.